Braking Systems Questions and Answers

Answer: C

Both shoes lead in forward rotation but both trail in reverse, so the brake is markedly weaker going backwards. It is used at the front where reverse braking matters less. Leading and trailing designs work equally in both directions. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Most errors here come from carrying across a result from a neighbouring case where it does not hold.

Answer: D

A disc caliper clamps the disc symmetrically and generates no self energising force, which is why disc brakes need a servo but behave predictably. Leading and trailing designs still have net self servo from the leading shoe. Predictability is the disc's virtue. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. Naming what changes and what stays the same is the reliable route through questions of this shape.

Answer: A

Without self servo the braking force is directly proportional to the pressure applied, which makes the brake linear and easy to modulate. The cost is a higher pedal effort, which the vacuum servo supplies. Predictability is what makes anti-lock control practical. Most errors here come from carrying across a result from a neighbouring case where it does not hold. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb.

Answer: B

The servo uses the pressure difference between manifold vacuum and atmosphere acting on a diaphragm to add force to the pedal input. The pedal linkage does multiply as well, so the last option is partly true, but the servo is the specific booster. Naming what changes and what stays the same is the reliable route through questions of this shape. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Working one numerical case through both cases side by side fixes the distinction better than any rule of thumb.

Answer: C

A throttled petrol engine produces substantial manifold depression at part throttle, which is tapped through a non return valve. Diesel engines have no throttle and need a pump. That is the essential difference between the two installations. Working the distinction through on a single concrete case fixes it more firmly than any rule of thumb. The order in which the effects act is what decides the outcome, so it is worth establishing first. The quantity that varies and the quantity that does not are worth naming before any substitution is attempted.

Answer: D

An unthrottled diesel produces almost no manifold vacuum, so a mechanical pump driven from the camshaft or the alternator supplies it. Electric pumps are used on stop start and hybrid vehicles. The pump is a common failure item. A symptom that appears under one condition and not another is what narrows the diagnosis quickly. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Checking the units of each quantity catches a wrong formula before the arithmetic begins.

Answer: A

The one way valve traps the depression so one or two assisted applications remain after the engine stops. Separate reservoirs are fitted to some vehicles but not to all. A failed valve is detected by the loss of that reserve. The order in which the effects act is what decides the outcome, so it is worth establishing first. The shared behaviour explains why these belong together and the differences explain why both exist. Framing the question as which quantity the change acts upon makes the answer follow without calculation.

Answer: B

Without assistance the driver must supply the whole effort and the pedal feels hard while the stopping distance lengthens. A sinking pedal indicates a master cylinder seal. Pulsation indicates a distorted disc. Checking which component actually carries the load settles most questions of this kind at once. Naming the cost of a choice alongside its benefit is what turns a fact into a design decision. Reading the definition literally, rather than recalling a summary, avoids the usual confusion.

Answer: C

Pumping exhausts the reserve, and with the pedal held down the engine is started, whereupon a working servo pulls the pedal down noticeably. A vacuum gauge is a useful confirmation. A sinking pedal is a master cylinder test, not a servo one. Tracing the requirement back to the physical constraint that produces it makes the answer follow. Reading the definition literally, rather than recalling a summary, avoids the usual confusion. The shared properties explain why these belong to one family, and the differences explain why more than one exists.

Answer: D

Fluid near a hot caliper can boil, and vapour is compressible, which produces a pedal that goes to the floor. Compressibility is precisely what must be avoided. Low viscosity matters at low temperature for anti-lock operation. The shared behaviour explains why these belong together and the differences explain why both exist. Most errors here come from carrying across a result from a neighbouring case where it does not hold. A limit that survives making every external component ideal is an intrinsic one, and worth knowing for that reason.